package com.wenhai.concurrency.aqs;

import java.io.Serializable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * @ClassName NonReentrantLock
 * @Description：基于 {@link AbstractQueuedSynchronizer} 实现的不可重入的独占锁
 * @Author 谢文海
 * @Date 2021/4/16 1:03
 * @Version 1.0
 **/
public class NonReentrantLock implements Lock, Serializable {

    private static class Sync extends AbstractQueuedSynchronizer{

        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        @Override
        public boolean tryAcquire(int acquires) {
            assert acquires == 1;
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }


        @Override
        public boolean tryRelease(int releases) {
            assert releases == 1;
            if (getState() == 0) {
                throw new IllegalMonitorStateException();
            }
            if (Thread.currentThread() != getExclusiveOwnerThread()) {
                throw new IllegalMonitorStateException();
            }
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }


        Condition newCondition() {
            return new ConditionObject();
        }
    }


    private final Sync sync = new Sync();


    @Override
    public void lock() {
        sync.acquire(1);

    }

    public boolean isLocked() {
        return sync.isHeldExclusively();
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);

    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }



}
